Thermodynamic stabilities of carbanionic .sigma. complexes. II. Simple ketones and their cyclic analogs

1975 ◽  
Vol 40 (10) ◽  
pp. 1499-1500 ◽  
Author(s):  
Robert M. Murphy ◽  
Claus A. Wulff ◽  
Michael J. Strauss
Keyword(s):  
Sigma Complexes

Interaction of heterocycles and nucleophiles. II. Sigma complexes formed from methoxide ion and Methoxy-3,5-dinitropyridines in dimethyl sulphoxide

1970 ◽  
Vol 23 (5) ◽  
pp. 957 ◽  
Author(s):  
MEC Biffin ◽  
J Miller ◽  
AG Moritz ◽  
DB Paul
Keyword(s):  
Dimethyl Sulphoxide ◽  
No Conversion ◽  
Solvation Effects ◽  
Sigma Complexes ◽  
Sigma Complex ◽  
Methoxide Ion ◽  
Rearrangement Reactions

Contrasting behaviour is observed when 2- and 4-methoxy-3,5-dinitropyridine interact with methoxide ion in dimethyl sulphoxide. The 4-methoxy compound affords both methine and acetal sigma complexes, the latter being thermodynamically more stable. The interconversion is catalysed by methanol. Labelling experiments have established that the sigma complex from the 2-methoxypyridine is formed by addition at C6; no conversion into the acetal could be effected. These observations are rationalized in terms of differential steric and solvation effects. Demethylation and rearrangement reactions of 4-methoxy-3,5-dinitropyridine are reported.

Hückel and Möbius Aromaticity in Charged Sigma Complexes

2019 ◽  
Vol 25 (31) ◽  
pp. 7457-7462 ◽  
Author(s):  
Michael Mauksch ◽  
Svetlana B. Tsogoeva
Keyword(s):  
Sigma Complexes

Approaches to Sigma Complexes via Displacement of Agostic Interactions: An Experimental and Theoretical Investigation

2017 ◽  
Vol 36 (15) ◽  
pp. 2736-2745 ◽  
Author(s):  
A. Ramaraj ◽  
K. Hari Krishna Reddy ◽  
Helena Keil ◽  
Regine Herbst-Irmer ◽  
Dietmar Stalke ◽  
...  
Keyword(s):  
Theoretical Investigation ◽  
Sigma Complexes

Structure and reactivity of aromatic .sigma.-complexes (cyclohexadienylium ions): a correlated experimental and theoretical study

1987 ◽  
Vol 109 (3) ◽  
pp. 882-892 ◽  
Author(s):  
F. Effenberger ◽  
F. Reisinger ◽  
K. H. Schoenwaelder ◽  
P. Baeuerle ◽  
J. J. Stezowski ◽  
...  
Keyword(s):  
Theoretical Study ◽  
Sigma Complexes
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